Place it right after the mistaken name is spoken, so the correction becomes the punch of the scene, then follow it with a short confused reaction such as Ceeday Huh to show the other person backtracking. If the mix-up is part of a longer argument, open with No No Wait Wait before this clip to set up the interruption.
About this sound
A short spoken clip, just over two seconds long, with a voice delivering the line about not calling him 'not mum' in a firm, corrective tone. It lands as funny and slightly awkward, like catching someone mid-mistake and shutting the mix-up down. The bluntness makes it feel protective and oddly quotable, perfect for a quick, deadpan reply.